Polymerizable fluorine-containing compound

ABSTRACT

A polymerizable fluorine-containing compound represented by formula (1), 
                         
wherein R 1  represents a polymerizable double-bond containing group, R 2  represents an acid-labile protecting group, R 3  represents a fluorine atom or fluorine-containing alkyl group, and W represents a bivalent linking group. This compound can provide a fluorine-containing polymer compound that has a weight-average molecular weight of 1,000-1,000,000 and contains a repeating unit represented by formula (2),
 
                         
wherein R 2 , R 3  and W are defined as above, each of R 4 , R 5  and R 6  independently represents a hydrogen atom, fluorine atom or monovalent organic group, at least two of R 4 , R 5  and R 6  may be combined to form a ring. This polymer compound can provide a resist composition capable of forming a pattern that is transparent to exposure light and superior in rectangularity.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 12/137,145, filedJun. 11, 2008, now U.S. Pat. No. 7,887,990. Priority is claimed fromJapanese patent application no. 2007-155165, filed Jun. 12, 2007.

BACKGROUND OF THE INVENTION

The present invention relates to a novel fluorine-containing compound, afluorine-containing polymer compound derived therefrom, a positive-typeresist composition using the polymer compound, and a pattern formingprocess by the resist composition.

In recent years, throughput of operation data and of two-dimensional andthree-dimensional image data has become enormous by the development ofdigital equipment, such as computer. In order to achieve a rapidprocessing of such information, there arises a demand for ahigh-capacity, high-speed memory and a high-performance microprocessor.Furthermore, a demand for processing ability on digital equipment isexpected to become increasingly high, due to a further acceleration ofbroadbandization along with the development of network such as Internet.

To satisfy this demand, various devices, such as semiconductor devices,are required to have a further high-density and a further highintegration. In particular, a demand for a photolithography that makesmicrofabrication possible has become strict year to year. For producinga DRAM having an integration degree of 1 G bits or more, it is necessaryto have a processing technology of a minimum line width of 0.13micrometers or less. In response to this, a photolithography using ArFexcimer laser (193 nm) is used. Furthermore, the development of aphotolithography using F₂ excimer laser (157 nm) is in progress for thepurpose of forming fine patterns.

In these wavelength regions, it is not possible to use novolac resinsand polyvinyl phenol resins, which have conventionally been used forresist compositions, since their light absorptions are too large. Thus,acrylic resins (see Japanese Patent Application Publication 10-161313)and cycloolefinic resins (see Japanese Patent Application Publication2000-089463) have been examined.

In the case of forming patterns by using a photoresist composition, atetramethylammonium aqueous solution (TMAH aqueous solution) isfavorably used, in place of organic solvent as a developing solution,due to environmental concern. Phenolic hydroxyl group, carboxyl group,and hexafluoroisopropanol group are known as functional groups that aresoluble in TMAH aqueous solution, that is, functional groups that make adevelopment by TMAH aqueous solution possible. In the case of usingwavelengths of ArF (193 nm) and F₂ (157 nm), aromatic ring has intenseabsorption bands at the both wavelength regions. Therefore, carboxylgroup or hexafluoroisopropanol is mainly in examination. In the case offorming particularly fine patterns, resins having ahexafluoroisopropanol group provide resist compositions that aresuperior in transparency, development property, and adhesion tosubstrate, thereby providing relatively good patterns. It is, however,known that a special synthesis technique is necessary for forming thoseresins. On the other hand, resins having a carboxyl group as thefunctional group swell in TMAH aqueous solution. Therefore, it isdifficult to obtain patterns as originally designed (see Japanese PatentApplication Publication 2007-086514).

As carboxylic compounds having a fluorine atom at α-position,2-fluorophenylacetic acid and its ester (see Japanese Patent ApplicationPublication 1-242551) and ethyl2,2-difluoro-3-hydroxy-3-phenylpropionate (see Tetrahedron Letters, Vol.25, No. 22, pp 2301-2302, 1984) are known.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide (a) a resistcomposition capable of forming a pattern that is transparent to exposurelight and superior in rectangularity by providing a fluorine-containingpolymer compound, which constitutes the resist composition used forforming patterns by using a high-energy ray of 300 nm or shorter orelectron beam, with a novel carboxyl-containing structure, and (b) afluorine-containing compound that is useful for introducing thestructure into the fluorine-containing polymer compound.

The present inventors have conducted en eager examination on solubilityof a resist film derived from a fluorine-containing polymer compoundhaving a carboxyl group as an acid-decomposing moiety in its repeatingunit, in TMAH aqueous solution. With this, we have found that the resistfilm dissolves at its exposed portion without having swelling at itsunexposed portion by introducing a fluorine atom at α-position of thecarboxyl group, thereby forming patterns as originally designed. Uponthis, we also have found a novel, polymerizable, fluorine-containingcompound that is useful for introducing a fluorine atom into α-positionof the carboxyl group of the fluorine-containing polymer compound.

Although the fluorine-containing polymer compound, which is an importantcomponent of the resist composition of the present invention, does notcontain a hetero atom, such as sulfur or phosphorus, in itsacid-decomposing moiety, it is possible to increase acidity of theacid-decomposing moiety, thereby easily eliminating the acid-labileprotecting group.

According to the present invention, there is provided afluorine-containing compound represented by formula (1),

wherein R¹ represents a polymerizable double-bond containing group, R²represents an acid-labile protecting group, R³ represents a fluorineatom or fluorine-containing alkyl group, and W represents a bivalentlinking group.

According to the present invention, there is provided afluorine-containing polymer compound comprising a repeating unit (a)represented by formula (2),

wherein R², R³ and W are defined as in formula (1), each of R⁴, R⁵ andR⁶ independently represents a hydrogen atom, fluorine atom or monovalentorganic group, and at least two of R⁴, R⁵ and R⁶ may be combined to forma ring,

wherein the fluorine-containing polymer compound has a weight-averagemolecular weight of 1,000 to 1,000,000.

A partial structure R¹—W— in formula (1) may include a group selectedfrom the group consisting of the following groups,

In formulas (1) and (2), W may represent a bivalent linking groupselected from the group consisting of a single bond, —(CR⁷R⁸)_(n)—(wherein n represents an integer of 1-10, each of R⁷ and R⁸independently represents a monovalent organic group, and R⁷ and R⁸ maybe combined to form a ring), —O—, —C(═O)—, —C(═O)O—, —O—C(═O)—, abivalent alicyclic hydrocarbon group, a bivalent aromatic hydrocarbongroup, a thioether group, an ester group, an amide group, a sulfonamidegroup, a urethane group, a urea group, and combinations of these.

The fluorine-containing compound may be selected from the groupconsisting of the following compounds,

wherein R² is defined as above, R³ represents a fluorine atom ortrifluoromethyl group, R⁷ represents a hydrogen atom or astraight-chain, branched or cyclic alkyl or fluoroalkyl group, R⁸represents a straight-chain, branched or cyclic alkyl or fluoroalkylgroup, and R⁷ and R⁸ may be combined to form a ring.

The fluorine-containing polymer compound may include a structure formedby cleavage of a polymerizable double bond of a compound selected fromthe group consisting of the above seven compounds.

In the above seven formulas, each of R⁷ and R⁸ independently mayrepresent a C₁-C₄ straight-chain or branched alkyl or fluoroalkyl groupor a C₃-C₁₀ cyclic alkyl or fluoroalkyl group, or R⁷ and R⁸ may bebonded together to form a C₄-C₈ alicyclic hydrocarbon group.

In the above seven formulas, R⁷ may represent a hydrogen atom or amonovalent organic group selected from the group consisting of methylgroup, ethyl group, propyl group, butyl group, cyclopentyl group,cyclohexyl group, norbornyl group, adamantyl group, trifluoromethylgroup, 2,2,2-trifluoroethyl group, 1-(trifluoromethyl)ethyl group, and3,3,3-trifluoropropyl group, and R⁸ may represent a monovalent organicgroup selected from the group consisting of methyl group, ethyl group,propyl group, butyl group, cyclopentyl group, cyclohexyl group,norbornyl group, adamantyl group, trifluoromethyl group,2,2,2-trifluoroethyl group, 1-(trifluoromethyl)ethyl group, and3,3,3-trifluoropropyl group. Alternatively, R⁷ and R⁸ may be bondedtogether to form a cyclopentyl group, cyclohexyl group or cycloheptylgroup.

In formulas (1) and (2), R² may be a monovalent organic group selectedfrom the group consisting of R¹¹—O—C(═O)—, R¹¹—O—CHR¹²—, CR¹³R¹⁴R¹⁵—,SiR¹³R¹⁴R¹⁵—, and R¹¹—C(═O)—, where R¹¹ represents an alkyl group,alicyclic hydrocarbon group, or aryl group; R¹² represents a hydrogenatom, alkyl group, alicyclic hydrocarbon group, alkenyl group, aralkylgroup, alkoxy group, or aryl group; each of R¹³, R¹⁴ and R¹⁵independently represents an alkyl group, alicyclic hydrocarbon group,alkenyl group, aralkyl group, or aryl group; and at least two groups ofR¹³, R¹⁴ and R¹⁵ may be combined to form a ring.

In formula (1), R² may represent a methoxymethyl or t-butyl group.

A partial structure in formula (2), which is represented by formula(9-1),

may include a structure formed by cleavage of a polymerizable doublebond of a group selected from the group consisting of the followinggroups,

The fluorine-containing polymer compound may include a structure formedby cleavage of a polymerizable double bond of a compound selected fromthe group consisting of the following compounds,

wherein R² and R³ are defined as in formula (1), and R⁷ and R⁸ aredefined as above.

The fluorine-containing polymer compound may further include a repeatingunit having a side chain with a lactone ring.

The fluorine-containing polymer compound may further include a repeatingunit (b) derived from a polymerizable monomer selected from the groupconsisting of acrylates, fluorine-containing acrylates, methacrylates,fluorine-containing methacrylates, styrene compounds,fluorine-containing styrene compounds, vinyl ethers, fluorine-containingvinyl ethers, allyl ethers, fluorine-containing allyl ethers,acrylamides, methacrylamides, vinyl esters, allyl esters, olefins,fluorine-containing olefins, norbornene compounds, fluorine-containingnorbornene compounds, sulfur dioxide, and vinyl silanes.

The fluorine-containing polymer compound may further include a repeatingunit (b), and the repeating unit (a) represented by formula (2) and therepeating unit (b) may respectively be in 0.1-99.9 mol % and 99.9-0.1mol %, based on a total mole number of all repeating units contained inthe fluorine-containing polymer compound.

According to the present invention, there is provided a resistcomposition including the fluorine-containing polymer; an acidgenerator; and a solvent.

According to the present invention, there is provided a process forforming a pattern, including the steps of:

(a) applying the resist composition on a substrate to form a resistfilm;

(b) exposing the resist film to a high-energy ray having a wavelength of300 nm or shorter or electron beam through a photomask;

(c) heating the exposed resist film; and

(d) developing the heated resist film.

The process may further include the step of (e) heating the resist film,between the steps (a) and (b).

In step (b), the high-energy ray may be a F₂ excimer laser, ArF excimerlaser, KrF excimer laser, or soft X-ray.

According to the present invention, there is provided an electronicdevice including a pattern formed by the process.

DETAILED DESCRIPTION

In the specification and the claims, alkyl group is defined ascontaining straight-chain, branched and cyclic alkyl groups. Cyclicalkyl group is defined as a part of alicyclic group or alicyclichydrocarbon group. The term of “lower” as in lower alkyl group and othergroups refers to a carbon atom number of 1-4. However, the term of“lower” as to cyclic alkyl group refers to one having a cyclic structureof a carbon atom number of 3-10, and cyclic alkyl group may have a loweralkyl group (e.g., methyl group, ethyl group, propyl group, butyl group,cyclopentyl group, cyclohexyl group, norbornyl group, adamantyl group,trifluoromethyl group, 2,2,2-trifluoroethyl group,1-(trifluoromethyl)ethyl group and 3,3,3-trifluoropropyl group) as asubstituent. Hereinafter, when a compound having isomers is exemplified,only its typical name and structure may be described for simplification,but it is defined as including all of its isomers.

In the specification, halogen refers to fluorine, chlorine, bromine oriodine.

A resist composition of the present invention provides an outstandingeffect. That is, a portion of the resist film exposed to a high-energyray having a wavelength of 300 nm or shorter or electron beam becomessoluble in a TMAH aqueous solution, and the resulting pattern (unexposedportion) shows a superior rectangularity. In case that thefluorine-containing compound represented by formula (1) contains anacid-labile protecting group (e.g., acetal group) having a chemicallyamplifying function, the resist composition derived from suchfluorine-containing compound shows transparency and a superiorrectangularity of the pattern, even if the resist film is exposed to ahigh-energy ray having a wavelength of 200 nm or shorter or electronbeam. Furthermore, a fluorine-containing compound of the presentinvention has an advantageous effect in which an acid-labile protectinggroup can easily and efficiently be introduced into afluorine-containing polymer, which constitutes a resist composition ofthe present invention.

Thus, a resist composition of the present invention can preferably beused as a positive-type resist composition, particularly as achemically-amplified resist composition by containing an acid-labileprotecting group. A fluorine-containing polymer compound of the presentinvention can preferably be used for such resist composition.Furthermore, a fluorine-containing compound of the present invention isone suitable for introducing an acid-labile protecting group into thefluorine-containing polymer compound.

In the following, the present invention is exemplarily described indetail by embodiments. The present invention is, however, not limited tothe embodiments. A skilled person in the art may suitably conduct amodification, improvement or the like on the following embodimentswithout deviating from the gist of the present invention, and suchmodification, improvement or the like is in the scope of the presentinvention.

The fluorine-containing polymer compound represented by formula (2) ofthe present invention is one having a polymer skeleton formed by ahomopolymerization through cleavage of a polymerizable double bond ofthe fluorine-containing compound represented by formula (1) or acopolymerization therethrough with another monomer having apolymerizable double bond.

As shown by formula (2), the fluorine-containing polymer compound of thepresent invention is characterized in that a chain skeleton formedthrough cleavage of the polymerizable double bond is bonded to acarboxyl group (COOR²) through a bivalent linking group W and that thiscarboxyl group has an acid-labile protecting group R² through ester bondand is bonded to the bivalent linking group W through α-position carbon,to which a fluorine atom and a fluorine atom or fluorine-containingalkyl group R³ are bonded.

Fluorine-Containing Polymer Compound

The fluorine-containing polymer represented by formula (2) is a resin ofwhich rate of dissolution increases in alkali developing solution by anaction of acid, and which has a group (acid-decomposing group) that isdecomposed by an action of acid and becomes alkali-soluble. Of theacid-decomposing group, a leaving moiety is referred to as anacid-labile protecting group.

As stated above, R³ of the fluorine-containing polymer compound is afluorine atom or fluorine-containing alkyl group. Although thisfluorine-containing alkyl group is not particularly limited, it may havea carbon atom number of 1-12, preferably 1-3. Its examples includetrifluoromethyl group, pentafluoroethyl group, 2,2,2-trifluoroethylgroup, n-heptafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group,3,3,3-trifluoropropyl group, and hexafluoroisopropyl group. R³ is morepreferably a fluorine atom or trifluoromethyl group.

The purpose of introducing an acid-labile protecting group into thefluorine-containing polymer compound, which constitutes a main componentof the resist composition, is to exhibit a positive-typephotosensitivity by the acid-labile protecting group and to exhibit asolubility of the resist in an alkali aqueous solution after exposure toa high-energy ray (e.g., far-ultraviolet ray, excimer laser, and X-ray)having a wavelength of 300 nm or shorter or electron beam. It ispossible to change and adjust polarity of the polymer terminal bychanging the type of the acid-labile protecting group or the ratio ofthe acid-labile protecting group to a stable group (i.e., a group ofwhich terminal is not an acid-labile protecting group definedhereinafter as R²). With this, it is possible to suitably adjustsolubility in solvent, coatability onto substrate, surface tension,dispersibility of the acid generator, acid diffusion rate, etc. Afluorine-containing polymer compound of the present invention with alarge number of fluorine atoms in the molecule can improve the resistfilm in transparency. In contrast, one with a cyclic structure canprovide the resist film with characteristics such as etching resistanceand high glass transition point. Thus, it is possible to use differentmolecular structures of the polymer compound for different purposes.

Examples of the acid-labile protecting group R² include R¹¹—O—C(═O)—,R¹¹—O—CHR¹²—, CR¹³R¹⁴R¹⁵—, SiR¹³R¹⁴R¹⁵—, and R¹¹—C(═O)—. Of these,R¹¹—O—C(═O)—, R¹¹—O—CHR¹²— and CR¹³R¹⁴R¹⁵— function as chemicallyamplified type. Therefore, these three groups are particularlypreferable for producing a resist composition to be used in a patternforming process in which exposure is conducted by a high-energy ray.

R¹¹ represents an alkyl group, alicyclic hydrocarbon group, or arylgroup (aromatic hydrocarbon group). R¹² represents a hydrogen atom,alkyl group, alicyclic hydrocarbon group, alkenyl group, aralkyl group,alkoxy group, or aryl group. Each of R¹³, R¹⁴ and R¹⁵ independentlyrepresents an alkyl group, alicyclic hydrocarbon group, alkenyl group,aralkyl group, or aryl group. At least two groups of R¹³, R¹⁴ and R¹⁵may be combined to form a ring.

The alkyl group for R¹¹ to R¹⁵ is preferably one having a carbon numberof 1-4, such as methyl group, ethyl group, propyl group, isopropylgroup, n-butyl group, sec-butyl group, and tert-butyl group. Thealicyclic hydrocarbon group therefor may be one having a carbon numberof 3-30, such as cyclopropyl group, cyclopentyl group, cyclohexyl group,adamantyl group, norbornyl group, bornyl group, tricyclodecanyl group,dicyclopentenyl group, norbornaneepoxy group, menthyl group, isomenthylgroup, neomenthyl group, tetracyclododecanyl group, and steroid residue.The alkenyl group for R¹² to R¹⁵ is preferably one having a carbonnumber of 2-4, such as vinyl group, propenyl group, allyl group, andbutenyl group. The aryl group for R¹¹ to R¹⁵ is preferably one having acarbon number of 6-14, such as phenyl group, xylyl group, tolyl group,cumenyl group, naphthyl group, and antracenyl group, and these groupsmay have substituents. The aralkyl group for R¹² to R¹⁵ may be onehaving a carbon number of 7-20, optionally having a substituent.Examples of the aralkyl group include benzyl group, phenethyl group, andcumyl group.

Examples of optional substituents of the organic groups R¹¹ to R¹⁵include hydroxyl group, halogen atoms, nitro group, cyano group, theabove-exemplified alkyl groups and alicyclic hydrocarbon groups, alkoxygroups (e.g., methoxy group, ethoxy group, hydroxyethoxy group, propoxygroup, hydroxypropoxy group, n-butoxy group, isobutoxy group, sec-butoxygroup, and tert-butoxy group), alkoxycarbonyl groups (e.g.,methoxycarbonyl group and ethoxycarbonyl group), aralkyl groups (e.g.,benzyl group, phenethyl group, and cumyl group), acyl groups (e.g.,aralkyloxy group, formyl group, acetyl group, butyryl group, benzoylgroup, cyanamyl group, and valeryl group), acyloxy groups (e.g.,butyloxy group), the above-exemplified alkenyl groups, alkenyloxy groups(e.g., vinyloxy group, propenyloxy group, allyloxy group, and butenyloxygroup), the above-exemplified aryl groups, aryloxy groups (e.g., phenoxygroup), and aryloxycarbonyl groups (e.g., benzoyloxy group).

Further examples of the optional substituents of R¹¹ to R¹⁵ includelactone groups represented by the following formulas (3-1) and (3-2),

wherein R^(a) represents a C₁-C₄ alkyl or perfluoroalkyl group. Each ofR^(b)'s independently represents a hydrogen atom, C₁-C₄ alkyl orperfluoroalkyl group, hydroxy group, carboxyl group, alkyloxycarbonylgroup or alkoxy group, and n represent an integer of 1-4.

In the following, specific examples of the above-mentioned acid-labileprotecting group R² are shown.

Examples of the alkoxycarbonyl group R¹¹—O—C(═O)— includetert-butoxycarbonyl group, tert-amyloxycarbonyl group, methoxycarbonylgroup, ethoxycarbonyl group, i-propoxycarbonyl group,cyclohexyloxycarbonyl group, isobornyloxycarbonyl group, andadamantaneoxycarbonyl group.

Examples of the acetal group R¹¹—O—CHR¹²— include methoxymethyl group,ethoxymethyl group, 1-ethoxyethyl group, 1-butoxyethyl,1-isobutoxyethyl, 1-cyclohexyloxyethyl group, 1-benzyloxyethyl group,1-phenethyloxypropyl group, 1-ethoxybutyl group, 1-cyclohexyloxyethylgroup, 1-ethoxyisobutyl group, 1-methoxyethoxymethyl group,tetrahydropyranyl group and tetrahydrofuranyl group. Further examplesinclude acetal groups obtained by adding vinyl ethers to hydroxy group.

Examples of the tertiary hydrocarbon group CR¹³R¹⁴R¹⁵— includetert-butyl group, tert-amyl group, 1-dimethylpropyl group,1-ethyl-1-methylpropyl group, 1,1-dimethylbutyl group,1-ethyl-1-methylbutyl group, 1,1-diethylpropyl group,1,1-dimethyl-1-phenylmethyl group, 1-methyl-1-ethyl-1-phenylmethylgroup, 1,1-diethyl-1-phenylmethyl group, 1-methylcyclohexyl group,1-ethylcyclohexyl group, 1-methylcyclopentyl group, 1-ethylcyclopentylgroup, 1-isobornyl group, 1-methyladamantyl group, 1-ethyladamantylgroup, 1-isopropyladamantyl group, 1-isopropylnorbornyl group, and1-isopropyl-4-methylcyclohexyl group.

In the following, specific examples of the acid-labile protecting groupR² containing an alicyclic hydrocarbon group are shown.

In the above formulas (4-1) and (4-2), methyl groups (CH₃) mayindependently be replaced with ethyl groups. As mentioned above, atleast one of the ring carbons may have at least one substituent.

Examples of the silyl group SiR¹³R¹⁴R¹⁵— include trimethylsilyl group,ethyldimethylsilyl group, methyldiethylsilyl group, triethylsilyl group,i-propyldimethylsilyl group, methyldi-i-propylsilyl group,tri-i-propylsilyl group, tert-butyldimethylsilyl group,methyldi-tert-butylsilyl group, tri-tert-butylsilyl group,phenyldimethylsilyl group, methyldiphenylsilyl group, and triphenylsilylgroup.

Examples of the acyl group R¹¹—C(═O) include acetyl group, propionylgroup, butyryl group, heptanoyl group, hexanoyl group, valeryl group,pivaloyl group, isovaleryl group, lauryloyl group, myristoyl group,palmitoyl group, stearoyl group, oxalyl group, malonyl group, succinylgroup, glutaryl group, adipoyl group, piperoyl group, suberoyl group,azelaoyl group, sebacoyl group, acryloyl group, propioloyl group,methacryloyl group, crotonoyl group, oleoyl group, maleoyl group,fumaroyl group, mesaconoyl group, campholoyl group, benzoyl group,phthaloyl group, isophthaloyl group, terephthaloyl group, naphthoylgroup, toluoyl group, hydroatropoyl group, atropoyl group, cinnamoylgroup, furoyl group, thenoyl group, nicotinoyl group, and isonicotinoylgroup. Furthermore, it is also possible to use ones in which fluorineatoms have been substituted for a part or entirety of hydrogen atoms ofthese acid-labile protecting groups.

The acid-labile protecting group R² containing a lactone ring isexemplified, as shown in the following formulas (5), (6) and (7).

In formulas (5), (6) and (7), methyl groups (CH₃) may independently bereplaced with ethyl groups.

In the case of using ArF excimer laser as alight source for exposure,preferable examples of the acid-labile protecting group R² are tertiaryalkyl groups (e.g., tert-butyl group and tert-amyl group), alkoxyethylgroups (e.g., 1-ethoxyethyl group, 1-butoxyethyl group, 1-isobutoxyethylgroup, and 1-cyclohexyloxyethyl group), and alkoxymethyl groups (e.g.,methoxymethyl group and ethoxymethyl group), and moreover theabove-mentioned alicyclic hydrocarbon groups (e.g., adamantyl group andisobornyl group), acid-labile protecting groups containing alicyclichydrocarbon groups (e.g., 1-methylcyclopentane, methyladamantyl group,ethyladamantyl group, methylisobornyl group and ethylisobornyl group)and lactones.

The bivalent linking group W in formula (1) or (2) may be selected froma single bond, —(CR⁷R⁸)_(n)— (wherein n represents an integer of 1-10,each of R⁷ and R⁸ independently represents a monovalent organic group,and R⁷ and R⁸ may be combined to form a ring), —O—, —C(═O)—, —C(═O)O—,—O—C(═O)—, a bivalent alicyclic hydrocarbon group, a bivalent aromatichydrocarbon group, a thioether group, an ester group, an amide group, asulfonamide group, urethane group, a urea group, and combinations ofthese.

The bivalent alicyclic hydrocarbon group may be a group obtained byremoving two hydrogen atoms from an alicyclic compound (e.g., norbornaneand adamantane). The bivalent aromatic hydrocarbon group may be a groupobtained by removing two hydrogen atoms from an aromatic compound (e.g.,benzene).

The linking group W as a combination of the above-mentioned groups maybe —(CR⁷R⁸)_(m)—C(═O)—O—(CR⁷R⁸)_(n)— or —(CR⁷R⁸)_(m)—(CR⁷R⁸)_(n)—, whereeach of m and n independently represents an integer of 0-10, m ispreferably 0, n is preferably 1, and, when each of R⁷ and R⁸ iscontained in a plural number, they may be the same or different.

The monovalent organic group R⁷ or R⁸ of the substituted methylene group—CR⁷R⁸— is not particularly limited. It may be a hydrogen atom, hydroxygroup, or a C₁-C₃₀ monovalent organic group selected from alkyl groups,alicyclic hydrocarbon groups, substituted alkyl groups, alkoxy groups,aryl groups, and condensed polycyclic aromatic groups. These monovalentorganic groups can have fluorine atom, oxygen atom, sulfur atom,nitrogen atom, and/or carbon-carbon double bond. Both of R⁷ and R⁸ maybe the same or different. R⁷ and R⁸ may be combined to form a ring. Thisring is preferably an alicyclic hydrocarbon group.

The alkyl group as R⁷ or R⁸ may be one having a carbon number of 1-30,preferably 1-12. For example, it is possible to cite methyl group, ethylgroup, n-propyl group, i-propyl group, n-butyl group, 1-methylpropylgroup, 2-methylpropyl group, tert-butyl group, n-pentyl group, i-pentylgroup, 1,1-dimethylpropyl group, 1-methylbutyl group, 1,1-dimethylbutylgroup, n-hexyl group, n-heptyl group, i-hexyl group, n-octyl group,i-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group,n-undecyl group, and n-dodecyl group. Of these, lower alkyl groups arepreferable. Particularly preferable ones are methyl group, ethyl group,n-propyl group, and i-propyl group.

Examples of the substituted alkyl group as R⁷ or R⁸ include ones inwhich at least one of hydrogen atoms of the alkyl group has beenreplaced with a C₁-C₄ alkoxy group, halogen atom, acyl group, acyloxygroup, cyano group, hydroxyl group, carboxyl group, alkoxycarbonylgroup, nitro group, or the like. A fluoroalkyl group in which at leastone of hydrogen atoms of the alkyl group has been replaced with afluorine atom(s) is preferable. Specific examples of the substitutedalkyl group include lower fluoroalkyl groups such as trifluoromethylgroup, pentafluoroethyl group, 2,2,2-trifluoroethyl group,n-heptafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group,3,3,3-trifluoropropyl group, and hexafluoroisopropyl group.

The alkoxy group as R⁷ or R⁸ may be a C₁-C₄ alkoxy group, such asmethoxy group, ethoxy group, propoxy group, and butoxy group.

The aryl group as R⁷ or R⁸ may be a C₁-C₃₀ aryl group. As a monocyclicaryl group, it is preferable to use one having a ring carbon number of3-12, more preferably 3-6. Examples include phenyl group, biphenylgroup, terphenyl group, o-tolyl group, m-tolyl group, p-tolyl group,p-hydroxyphenyl group, p-methoxyphenyl group, mesityl group, o-cumenylgroup, 2,3-xylyl group, 2,4-xylyl group, 2,5-xylyl group, 2,6-xylylgroup, 3,4-xylyl group, 3,5-xylyl group, o-fluorophenyl group,m-fluorophenyl group, p-fluorophenyl group, o-trifluoromethylphenylgroup, m-trifluoromethylphenyl group, p-trifluoromethylphenyl group,2,3-bis(trifluoromethyl)phenyl group, 2,4-bis(trifluoromethyl)phenylgroup, 2,5-bis(trifluoromethyl)phenyl group,2,6-bis(trifluoromethyl)phenyl group, 3,4-bis(trifluoromethyl)phenylgroup, 3,5-bis(trifluoromethyl)phenyl group, p-chlorophenyl group,p-bromophenyl group, and p-iodophenyl group.

The C₁-C₃₀, condensed polycyclic aromatic group as R⁷ or R⁸ may be amonovalent organic group, such as pentalenyl group, indenyl group,naphthyl group, azlenyl group, heptalenyl group, biphenylenyl group,indacenyl group, acenaphthylenyl group, fluorenyl group, phenarenylgroup, phenanthryl group, anthryl group, fluoranthenyl group,acephenanthrylenyl group, aceanthrylenyl group, triphenylenyl group,pyrenyl group, chrysenyl group, naphthacenyl group, picenyl group,perylenyl group, pentaphenyl group, pentacenyl group, tetraphenylenylgroup, hexaphenyl group, hexacenyl group, rubicenyl group, coronenylgroup, trinaphthylenyl group, heptaphenyl group, heptacenyl group,pyranthrenyl group, and ovalenyl group. It is possible to cite ones inwhich at least one hydrogen atom of these groups has been replaced witha fluorine atom(s) or a C₁-C₄ alkyl or fluorine-containing alkyl group,as preferable ones.

Examples of a monocyclic or polycyclic, heterocyclic group as R⁷ or R⁸having a ring atom number of 3-25 include pyridyl group, furyl group,thienyl group, pyranyl group, pyrrolyl group, thiantrenyl group,pyrazolyl group, isothiazolyl group, isoxazolyl group, pyrazinyl group,pyrimidinyl group, pyridadinyl group, tetrahydropyranyl group,tetrahydrofuranyl group, tetrahydrothiopyranyl group,tetrahydrothiofuranyl group, 3-tetrahydrothiophen-1,1-dioxide group, andheterocyclic groups in which at least one hydrogen atom of the ring hasbeen replaced with an alkyl group, alicyclic hydrocarbon group, arylgroup or heterocyclic group. Of these, ones having a monocyclic orpolycyclic ether ring or lactone ring are preferable, such as thefollowing,

wherein each of R^(a) and R^(b) independently represents a hydrogen atomor C₁-C₄ alkyl group, and n represents an integer of 2-4.

As R⁷ and R⁸, a simple alicyclic hydrocarbon group or a combinedalicyclic hydrocarbon group formed by simple alicyclic hydrocarbongroups that are combined together through carbon atoms may have amonocyclic or polycyclic structure. Specifically, these groups may havea monocyclo, bicyclo, tricyclo or tetracyclo structure of a carbonnumber of at least 3. The carbon number is preferably 3-30, morepreferably 3-25. These alicyclic hydrocarbon groups may havesubstituents.

The alicyclic hydrocarbon group of monocyclic structure has a ringcarbon number of preferably 3-12, more preferably 3-7. Its preferableexamples include cyclopropyl group, cyclobutyl group, cyclopentyl group,cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclodecanylgroup, cyclododecanyl group, and 4-tert-butylcyclohexyl group. Examplesof the alicyclic hydrocarbon group of polycyclic structure include thosehaving a ring carbon number of 7-15, such as adamantyl group,noradamantyl group, decaline residue, tricyclodecanyl group,tetracyclododecanyl group, norbornyl group, and cedrol group. Thealicyclic hydrocarbon group may be a spiro ring, preferably having acarbon number of 3-6. Its preferable examples include adamantyl group,decaline residue, norbornyl group, cedrol group, cyclohexyl group,cycloheptyl group, cyclooctyl group, cyclodecanyl group, cyclododecanylgroup, and tricyclodecanyl group. At least one hydrogen atom of the ringcarbons or linking groups of these organic groups may independently bereplaced with at least one C₁-C₂₅ alkyl or substituted alkyl group,hydroxy group, alkoxy group, carboxyl group, alkoxycarbonyl group, or agroup in which at least one hydrogen atom of these groups has beenreplaced with at least one fluorine atom or trifluoromethyl group.

The alkyl group is preferably a lower alkyl group, more preferably analkyl group selected from methyl group, ethyl group, propyl group, andisopropyl group. The substituted alkyl group may have a substituent thatis a hydroxy group, halogen atom or alkoxy group. The alkoxy group maybe a C₁-C₄ alkoxy group such as methoxy group, ethoxy group, propoxygroup and butoxy group. The alkoxycarbonyl group may be amethoxycarbonyl group, ethoxycarbonyl group, or isopropoxycarbonylgroup.

Specifically, the linking group W may be a single bond, —O—, —C(═O)—O—,—CH₂—O—, —O—CH₂—, —CH₂—C(═O)—O—, —C(═O)—O—CH₂, —CH₂—O—CH₂—,—CH₂—C(═O)—O—CH₂—, —C(═O)—O—CR⁷R⁸—, or —C₆H₄—O—CR⁷R⁸—. Herein, each ofR⁷ and R⁸ is preferably and independently a hydrogen atom, fluorineatom, alkyl group, substituted alkyl group, or alicyclic hydrocarbongroup. At least one hydrogen atom of these groups may be replaced withat least one fluorine atom. Of these examples, a more preferable one is—C(═O)—O—CR⁷R⁸— where each of R⁷ and R⁸ is independently a hydrogen atomor lower alkyl group.

A structure of the fluorine-containing polymer compound is derived fromthe polymerizable double-bond containing group and is represented byformula (9),

where each of R⁴ and R⁶ is independently a hydrogen atom, alkyl group oralicyclic hydrocarbon group. R⁵ represents a hydrogen atom, cyano group,halogen atom, or alkyl group.

This alkyl group may be a substituted or unsubstituted one having acarbon atom number of 1-4. Examples of the alkyl group include methylgroup, ethyl group, n-propyl group, isopropyl group, n-butyl group,isobutyl group, sec-butyl group, and tert-butyl group. The alkyl groupmay have a substituent that is a C₁-C₄ alkoxy group, halogen atom, acylgroup, acyloxy group, cyano group, hydroxy group, carboxyl group,alkoxycarbonyl group, or nitro group.

The polymerizable double-bond containing group R¹ of thefluorine-containing compound represented by formula (1) may be (a) aC₂-C₁₀ alkenyl group, such as vinyl group, allyl group, isopropenylgroup, 1-propenyl group, 1-butenyl group, 1-pentenyl group,1-methyl-1-propenyl group, 1-methyl-1-butenyl group, 2-methyl-1-butenylgroup, 1-methyl-1-pentenyl group, 2-methyl-1-pentenyl group,3-methyl-1-pentenyl group, and 4-methyl-1-pentenyl group; (b) a C₂-C₁₀fluorine-containing alkenyl group, such as perfluoroallyl group,3-trifluoromethyl-2-propenyl group, 1-perfluorobutenyl group,1-perfluoropentenyl group, 1-trifluoromethyl-1-butenyl group,2-trilfluoromethyl-1-butenyl group, 3-trifluoromethyl-1-butenyl group,and 4-trifluoromethyl-1-butenyl group; or (c) a C₂-C₁₀ alkenyl grouphaving a substituent that is a substituted or unsubstituted phenylgroup, such as 1-phenyl-1-propenyl group, 2-phenyl-1-propenyl group,3-phenyl-1-propenyl group, 1-phenyl-1-butenyl group, 3-phenyl-1-butenylgroup, and 4-phenyl-1-butenyl group; or (d) a C₂-C₁₀ alkenyl grouphaving a substituent that is an alicyclic hydrocarbon group, cycloethergroup, lactone group, or an alicyclic hydrocarbon group that is anorbornene skeleton, norbornane skeleton, isobornyl skeleton,tricyclodecane skeleton, tetracyclododecane skeleton, adamantaneskeleton, or the like.

As R⁴, R⁵ or R⁶, a simple alicyclic hydrocarbon group or a combinedalicyclic hydrocarbon group formed by simple alicyclic hydrocarbongroups that are combined together through carbon atoms may have amonocyclic or polycyclic structure. Specifically, these groups may havea monocyclo, bicyclo, tricyclo or tetracyclo structure of a carbonnumber of at least 5. The carbon number is preferably 6-30, morepreferably 7-25. These alicyclic hydrocarbon groups may havesubstituents.

Examples of the alicyclic hydrocarbon group of R⁴, R⁵ or R⁶ may be thesame as those of that of R⁷ or R⁸.

In the structure represented by formula (9) of the fluorine-containingpolymer compound, two of R⁴, R⁵ and R⁶ may be combined together, therebyforming the following exemplary ring structure represented by formula(10),

where R⁵ represents a hydrogen atom, cyano group, halogen atom, or alkylgroup; and A represents a group containing two carbon atoms C—C combinedtogether, for forming an alicyclic structure.

This alicyclic structure may have a C₃-C₁₀ monocyclic or polycyclicstructure, such as cyclopentane, cyclohexane, cycloheptane, norbornane,or a structure in which at least one hydrogen atom of these structureshas been replaced with at least one lower alkyl or lower fluoroalkylgroup.

Furthermore, the polymerizable double-bond containing group R¹ of thefluorine-containing compound may have a structure represented by thefollowing formula (10-1) or (10-2) or a structure of vinylphenyl group,

where formulas (10-1) and (10-2) are shown in the form of repeating unitafter cleavage of the double bond, each of R's independently representsa hydrogen atom, halogen atom, or cyano group, and n represents aninteger of 1-4.

The polymerizable double-bond containing group R¹ of thefluorine-containing compound is preferably a structure represented byCH₂═CH—, CH₂═C(CH₃)—, CH₂═C(CF₃)— or CH₂═C(CH₂OH)—, or a structurerepresented by one of the following formulas (10-3) to (10-6),

where formulas (10-3) to (10-6) are shown in repeating unit aftercleavage of the double bond. Of these, CH₂═CH—, CH₂═C(CH₃)—, andCH₂═C(CF₃)— are more preferable, and CH₂═C(CH₃)— is still morepreferable.

It is preferable that the following partial structure (9-1)

where all of the symbols are defined as in formula (2), contained in therepeating unit (a) represented by formula (2) has a structure obtainedby cleavage of the polymerizable double-bond of a group selected fromvinyloxy group, allyloxy group, acryloyloxy group, methacryloyloxygroup, α,α,α-trifluoroacryloyloxy group, norbornoyloxy group, andvinylphenoxy group, which are respectively shown as follows.

The fluorine-containing compound represented by formula (1) may have aformula selected from the following most preferable exemplary formulas,

wherein R² represents an acid-labile protecting group, R³ represents afluorine atom or trifluoromethyl group, R⁷ represents a hydrogen atom ora straight-chain, branched or cyclic alkyl or fluoroalkyl group, R⁸represents a straight-chain, branched or cyclic alkyl or fluoroalkylgroup, and R⁷ and R⁸ may be combined to form a ring.

In the above formulas, R³ is particularly preferably a fluorine atom.The alkyl or fluoroalkyl group of R⁷ and R⁸ is preferably a lower alkylor lower fluoroalkyl group. It is preferable that the alkyl group is acyclic alkyl group. It is preferable that R⁷ represents a hydrogen atom.It is particularly preferable that R³ represents a fluorine atom, R⁷represents a hydrogen atom or lower alkyl group, and R⁸ represents alower alkyl group. It is also preferable that R³ represents a fluorineatom, and R⁷ and R⁸ are bonded together to form a lower alicyclichydrocarbon group.

In the fluorine-containing polymer compound of the present invention,the molar ratio (copolymerization ratio) of the repeating unit (a) tothe repeating unit (b) derived from another copolymerizable monomer(comonomer) can suitably be set for adjusting resist dry etchingresistance, standard developing solution suitability, adhesion tosubstrate, resist profile, and resolving power, heat resistance,sensitivity and the like, which are general properties required forresists. The above-mentioned another copolymerizable monomer isdescribed in detail hereinafter in the section of “ANOTHER COMONOMER”.

The fluorine-containing polymer compound of the present invention may bea homopolymer of the repeating unit (a) or a copolymer in which themolar ratio of the repeating unit (a) to the repeating unit (b) is0.1-99.9%:99.9-0.1%, 1-99%:99-1%, or 10-90%:90-10%, preferably30-70%:70:30%, based on the total mol number of the repeating units (a)and (b). If the repeating unit (a) is in less than 0.1%, solubility upondevelopment may become inferior. If it is in greater than 99.9%,solubility adjustment may become difficult.

It is preferable that the repeating unit (b) derived from anothercomonomer is a first repeating unit derived from an acrylic ormethacrylic ester having a lactone group or a second repeating unitderived from an acrylic or methacrylic ester having a polar group. Inthis case, the content of the first repeating unit in thefluorine-containing polymer compound is preferably 10-60 mol %, morepreferably 20-50 mol %. The content of the second repeating unit thereinis preferably 1-50 mol %, more preferably 5-30 mol %. Furthermore, thefluorine-containing polymer compound may contain a third repeating unitthat contains no acid-labile protecting group and is derived from anacrylic or methacrylic ester with none of a polar group and a lactonegroup. In this case, the content of the third repeating unit therein ispreferably 1-70 mol %, more preferably 5-60 mol %.

The fluorine-containing polymer compound of the present invention may be1,000-1,000,000, preferably 2,000-500,000, in weight average molecularweight determined by gel permeation chromatography (GPC). If it is lessthan 1,000, the resist film may become insufficient in strength. If itis greater than 1,000,000, solubility in solvent may become too low.With this, it may become difficult to obtain a flat resist film.Dispersibility (Mw/Mn where Mw represents weight average molecularweight, and Mn represents number average molecular weight) is preferably1.01-5.00, more preferably 1.01-4.00, particularly preferably 1.01-3.00,the most preferably 1.10-2.50.

The process for polymerizing the fluorine-containing compound is notparticularly limited, as long as it is one generally used. It ispreferable to use radical polymerization or ion polymerization. In somecases, it is also possible to use coordination anion polymerization,living anion polymerization, cation polymerization, ring-openingmetathesis polymerization, vinylene polymerization or vinyl additionpolymerization.

The radical polymerization may be conducted by a known polymerizationmethod, such as bulk polymerization, solution polymerization, suspensionpolymerization or emulsion polymerization, in the presence of a radicalpolymerization initiator or radical initiating source, with abatch-wise, half-continuous or continuous operation.

The radical polymerization initiator is not particularly limited. As itsexamples, azo compounds, peroxide compounds and redox compounds arecited. In particular, preferable examples include azobisbutyronitrile,t-butylperoxypivalate, di-t-butylperoxide, i-butyrylperoxide,lauroylperoxide, succinic acid peroxide, dicinnamylperoxide,di-n-propylperoxydicarbonate, t-butylperoxyallyl monocarbonate, benzoylperoxide, hydrogen peroxide, and ammonium persulfate.

The reaction vessel used in the polymerization reaction is notparticularly limited. Furthermore, a polymerization solvent may be usedin the polymerization reaction. As the polymerization solvent, one thatdoes not interfere with the radical polymerization is preferable.Representative ones are ester solvents such as ethyl acetate and n-butylacetate; ketone solvents such as acetone and methyl isobutyl ketone;hydrocarbon solvents such as toluene and cyclohexane; and alcoholsolvents such as methanol, isopropyl alcohol and ethylene glycolmonomethyl ether. Furthermore, it is also possible to use solvents suchas water, ethers, cyclic ethers, fluorohydrocarbons, and aromatics.These solvents can be used singly or in combination of at least twotypes. Furthermore, it may be accompanied in use with a molecular weightadjusting agent such as mercaptan. The reaction temperature of thepolymerization reaction is suitably changed, depending on the radicalpolymerization initiator or radical polymerization initiating source. Ingeneral, 20-200° C. is preferable. In particular, 30-140° C. ispreferable.

It is possible to remove organic solvent or water from the obtainedsolution or dispersion of the fluorine-containing polymer compound byreprecipitation, filtration, heating distillation under reducedpressure, or the like.

Fluorine-Containing Monomer

The repeating unit represented by formula (2) of the fluorine-containingpolymer compound is formed by the production of a bivalent group throughcleavage of the polymerizable double bond of the fluorine-containingcompound (monomer) represented by formula (1). Thus, the abovedescription in the section of “FLUORINE-CONTAINING POLYMER COMPOUND”with respect to the polymerizable double bond for forming the chainskeleton moiety, the group containing the polymerizable double bond,each organic group, the linking group W, the acid-labile protectinggroup R² and the like corresponds directly to that of thefluorine-containing monomer and therefore is not repeated herein.

The process for producing the fluorine-containing compound representedby formula (1) is not particularly limited. For example, it can beproduced by a process represented by the following reaction formulas [1]to [4],

where R¹, R² and R³ are defined as in formula (1); R^(d) represents ahydrogen atom or monovalent organic group, and each of R^(e) and R^(f)independently represents a monovalent organic group; each of X and X′independently represents a halogen atom, trifluoromethanesulfonategroup, C₁-C₄ alkylsulfonate group or arylsulfonate group; W′ representsa bivalent linking group; and W′—O—CR^(d)R^(e) corresponds to W informula (1).

As each of R^(d) and R^(e) corresponds to R⁷ or R⁸, detailed descriptionof R^(d) and R^(e) is the same as that of R⁷ and R⁸. The monovalentorganic group as R^(d), R^(e) or R^(f) is preferably a lower alkyl orfluoroalkyl group, such as methyl group, ethyl group, propyl group,butyl group, cyclopentyl group, cyclohexyl group, norbornyl group,adamantyl group, trifluoromethyl group, 2,2,2-trifluoroethyl group,1-(trifluoromethyl)ethyl group, and 3,3,3-trifluoropropyl group. It ismore preferable that R^(d) and R^(e) are bonded together to form acyclopentyl group, cyclohexyl group, or cycloheptyl group.

The above process represented by reaction formulas [1] to [4] isdescribed in detail, as follows. At first, as shown in reaction formula[1], a fluorine-containing carboxylate (i) having an active halogen atomat α-position is reacted with a carbonyl compound (ii) in the presenceof Zn under an anhydrous condition (Reformatsky reaction), therebyobtaining a hydroxy carboxylate (iii). Then, as shown in reactionformula [2], the hydroxy carboxylate (iii) is reacted in solvent with ahalogen compound (iv) having a polymerizable double bond in the presenceof a base, thereby obtaining an unsaturated carboxylate (v). Then, asshown in reaction formula [3], the carboxylate (v) is hydrolyzed into anunsaturated carboxylic acid (vi) having a fluorine atom at α-position.At last, the obtained unsaturated carboxylic acid (vi) is reacted insolvent with a halogen compound (vii) in the presence of a base, therebyobtaining a fluorine-containing compound (viii). It is clear thatformula (viii) corresponds to formula (1) if “W′—O—CR^(d)R^(e)” isinterpreted as W.

The solvent used in the reaction of reaction formulas [1], [2] or [4] isnot particularly limited, as long as it is not active in the reaction.Its examples include aliphatic hydrocarbons such as pentane, hexane andheptane; aromatic hydrocarbons such as benzene, toluene and xylene;nitriles such as acetonitrile, propionitrile, phenylacetonitrile,isobutyronitrile, and benzonitrile; acid amides such asdimethylformamide, dimethylacetamide, methylformamide, formamide, andhexamethylphosphoric triamide, lower ethers such as tetrahydrofuran,1,2-dimethoxyethane, 1,4-dioxane, diethyl ether, 1,2-epoxyethane,1,4-dioxane, dibutyl ether, tert-butyl methyl ether, and substitutedtetrahydrofurans. Of these dimethylformamide and tetrahydrofuran arepreferable. These solvents can be used in combination. The amount of thesolvent may be about 1-100 parts by weight, preferably 1-10 parts byweight, relative to one part by weight of the starting material.

It is preferable to remove water as much as possible from the solvent tobe used in the reaction of reaction formula [1]. The water content ofthis solvent is more preferably 50 ppm or less.

It is also preferable to remove water as much as possible from thesolvent to be used in the reaction of reaction formulas [2] or [4]. Itis, however, not necessary to completely remove water from this solvent.Its water content close to that is generally contained in anindustrially available solvent is not problematic in conducting thereaction. Therefore, such solvent can be used without removing water.

It is preferable to activate zinc by a known method for its use in thereaction of reaction formula [1]. Its exemplary methods include a methodusing metallic zinc obtained by reducing a zinc salt (e.g., zincchloride) with potassium, magnesium, lithium or the like; a method foractivating metallic zinc by treating metallic zinc with hydrochloricacid; a method for activating zinc by treating metallic zinc with acopper salt or silver salt in acetic acid to convert metallic zinc intoan alloy of zinc and copper or silver; a method for activating zinc byultrasonic waves; a method for activating zinc by mixing metallic zincwith chlorotrimethylsilane in ether; and a method for activating zinc bybringing metallic zinc into contact with chloromethylsilane and a coppercompound in an aprotic organic solvent.

Zinc may have any form, such as powder, granule, aggregate, porous form,cutting scrap, or filament. The reaction temperature for conducting thereaction of reaction formula [1] may be about −78 to 120° C. Itsreaction time may be 10 minutes to 20 hours for convenience, although itvaries depending on the reaction agents. Its reaction pressure may bearound ordinary pressure. Its other reaction conditions may be the sameas those of known analogous reactions using metallic zinc therein.

Examples of the base used in the reactions of reaction formulas [2] and[4] include organic bases, such as trimethylamine, triethylamine,diisopropylethylamine, tri-n-propylamine, tri-n-butylamine,dimethyllaurylamine, dimethylaminopyridine, N,N-dimethylaniline,dimethylbenzylamine, 1,8-diazabicyclo[5,4,0]undec-7-ene,1,4-diazabicyclo[2,2,2]octane, pyridine, 2,4,6-trimethylpyridine,pyrimidine, pyridazine, 3,5-lutidine, 2,6-lutidine, 2,4-lutidine,2,5-lutidine, and 3,4-lutidine. Of these, triethylamine,diisopropylethylamine, dimethylaminopyridine,1,8-diazabicyclo[5,4,0]undec-7-ene, pyridine, and 2,6-lutidine arepreferable.

The amount of the base to be used in the reaction of reaction formula[2] or [4] may be 1 mol or greater, generally preferably 1-10 moles,particularly more preferably 1-5 moles, per mol of the substrate.

Similar to the reaction of reaction formula [1], the reactiontemperature for conducting the reactions of reaction formulas [2] to [4]may be about −78 to 120° C. Their reaction time may be 10 minutes to 20hours for convenience, although it varies depending on the reactionagents. Their reaction pressure may be around ordinary pressure. Theirother reaction conditions may be the same as those of known analogousreactions.

The reaction of reaction formula [3] is conducted by hydrolyzing thesubstrate (v) with water in the presence of a basic substance that maybe the above-mentioned organic base or an inorganic basic substance(e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, andcalcium hydroxide).

It is possible to conduct a purification operation (e.g., washing,separation of solvent, etc., and drying) after each reaction of reactionformulas [1] to [4].

In case that a fluorine-containing carboxylate having an acid-labileprotecting group is available (i.e., R^(f)=R² in formula (i)), it ispossible to obtain the target fluorine-containing compound representedby formula (viii) by conducting only the two reactions of reactionformulas [1] and [2].

Other Comonomers

The fluorine-containing polymer compound of the present invention isobtained by homopolymerization of the fluorine-containing compoundrepresented by formula (1) or by its copolymerization with at least onepolymerizable monomer (comonomer). In this polymerization, cleavage ofthe C—C double bond of the polymerizable double-bond containing group R¹of the fluorine-containing compound occurs to form the skeleton of thefluorine-containing polymer compound, but the rest of the structure ofthe fluorine-containing compound does not change.

Besides the repeating unit (a) represented by formula (2), thefluorine-containing polymer compound can contain various repeating unitsfor the purpose of adjusting dry etching resistance, standard developingsolution suitability, adhesion to substrate, resist profile, and generalcharacteristics (e.g., resolution, heat resistance and sensitivity)necessary for resist.

Such repeating units may be those corresponding to the after-mentionedmonomers, but are not limited to those. By containing such repeatingunits, it is possible to achieve fine adjustments of qualities necessaryfor the resin, particularly (1) solubility in coating solvent, (2) filmforming property (glass transition point), (3) alkali developmentproperty, (4) film decrease upon alkali development (hydrophilic orhydrophobic property and alkali-soluble group selection), (5) adhesionof the unexposed portion to substrate, and (6) dry etching resistance.

Examples of other comonomers copolymerizable with thefluorine-containing compound include the following compounds [1], [2]and [3].

[1] polymerizable compounds represented by formula (1) where R²represents a monovalent organic group containing no acid-labileprotecting group;

[2] polymerizable compounds represented by formula (1) where α-positionatom of the carboxylic moiety (COOR²) has at least one hydrogen atom;and

[3] polymerizable compounds represented by formula of R¹—W—Y where R¹and W are defined as in formula (1) and Y represents a monovalentorganic group containing no acid-labile protecting group.

The acid-labile protecting group in the compounds [1]-[3] is defined asin the fluorine-containing polymer compound. The above description withrespect to the monovalent organic groups R¹, R³, R⁴, R⁵ and R⁶ and thebivalent linking group W corresponds directly to that of the compounds[1] and [2] and therefore is not repeated herein.

Examples of the compounds [3] include acrylates, fluorine-containingacrylates, methacrylates, fluorine-containing methacrylates, styrenecompounds, fluorine-containing styrene compounds, vinyl ethers,fluorine-containing vinyl ethers, allyl ethers, fluorine-containingallyl ethers, acrylamides, methacylamides, vinyl esters, allyl esters,olefins, fluorine-containing olefins, norbornene compounds,fluorine-containing norbornene compounds, sulfur dioxide, and vinylsilanes. At least one monomer selected from these can be copolymerizedwith the fluorine-containing compound.

The above acrylates and methacrylates are not particularly limited withrespect to their ester moiety. Their examples include alkyl esters ofacrylic acid or methacrylic acid, such as methyl acrylate ormethacrylate, ethyl acrylate or methacrylate, n-propyl acrylate ormethacrylate, isopropyl acrylate or methacrylate, n-butyl acrylate ormethacrylate, isobutyl acrylate or methacrylate, tert-butyl acrylate ormethacrylate, amyl acrylate or methacrylate, n-hexyl acrylate ormethacrylate, n-octyl acrylate or methacrylate, 2-ethylhexyl acrylate ormethacrylate, benzyl acrylate or methacrylate, chlorobenzyl acrylate ormethacrylate, octyl acrylate or methacrylate, 2-hydroxyethyl acrylate ormethacrylate, 4-hydroxybutyl acrylate or methacrylate, 5-hydroxypentylacrylate or methacrylate, 2,2-dimethyl-3-hydroxypropyl acrylate ormethacrylate, trimethylolpropane monoacrylate or methacrylate,pentaerythritol monoacrylate or methacrylate, furfuryl acrylate ormethacrylate, tetrahydrofurfuryl acrylate or methacrylate, laurylacrylate or methacrylate, and 2-hydroxypropyl acrylate or methacrylate;acrylate or methacrylate containing an ethylene glycol, propylene glycolor tetramethylene glycol group; 3-oxocyclohexylacrylate or methacrylate,adamantyl acrylate or methacrylate, alkyladamantyl acrylate ormethacrylate, cyclohexyl acrylate or methacrylate, tricyclodecanylacrylate or methacrylate, and acrylates or methacrylates containing aring structure (e.g., norbornene ring); and the above-mentionedacrylates containing a trifluoromethyl group or cyano group atα-position.

The fluorine-containing acrylates or methacrylates contain fluorine attheir ester moiety and may have a cyano group at their α-position. It ispossible to use without a particular limitation fluorine-containingacrylates or methacrylates in which a part of the ester moiety of theabove-mentioned acrylates or methacrylates has been fluorinated. Inother words, they are acrylates or methacrylates having at their estermoiety a fluorine-containing alkyl group or a fluorine-containing ringstructure (e.g., fluorine-containing benzene ring, fluorine-containingcyclopentane ring, fluorine-containing cyclohexane ring,fluorine-containing cycloheptane ring, fluorine-containing norbornelgroup, and fluorine-containing adamantyl group) in which at least onehydrogen at their ring carbon(s) has been replaced with at least onefluorine atom or fluorine-containing alkyl group (e.g., trifluoromethylgroup). Furthermore, it is also possible to use acrylates ormethacrylates having at their ester moiety a fluorine-containingtert-butyl ester or a cyclohexyl group or norbornyl group containing ahexafluoroisopropanol group substituted.

Furthermore, preferable comonomers include an acrylate, methacrylate orα,α,α-trifluoroacrylate containing a lactone group. This lactone groupmay be any group containing a lactone structure. It is preferably agroup containing a five to seven-membered lactone structure. It ispreferably a group having a ring-fused structure (e.g., bicyclostructure and spiro structure) formed by a combination of another ringstructure with a five to seven-membered lactone structure. By containinga lactone ring, the resulting resist is improved in line edge roughnessand development defect.

The above lactone group may be selected from the structures representedby the following formulas (12-1) and (12-2),

where R^(a) represents a C₁-C₄ alkyl group or perfluoroalkyl group, eachof R^(b) independently represents a hydrogen atom, a C₁-C₄ alkyl groupor perfluoroalkyl group, a hydroxy group, a carboxyl group, analkyloxycarbonyl group, an alkoxy group or the like, and n represents aninteger of 1-4,

where each of R^(b) independently represents a hydrogen atom, a C₁-C₄alkyl group or perfluoroalkyl group, a hydroxy group, a carboxyl group,an alkyloxycarbonyl group, an alkoxy group or the like, and n representsan integer of 1-4.

Specific examples of the lactone group include the following formulas(13-1) to (13-6).

In the formulas (13-1) to (13-6), methyl groups (CH₃) may independentlybe replaced with ethyl groups.

The vinyl ethers or allyl ethers as the comonomers may be those having aC₁-C₃₀ alkyl group, fluoroalkyl group or alicyclic hydrocarbon group asa substituent. These groups preferably contain a halogen atom, hydroxygroup, amino group, aryl group, alkyl group or alicyclic hydrocarbongroup as a substituent. The vinyl ethers and allyl ethers areexemplified, as follows.

Specific examples of alkyl vinyl ether include methyl vinyl ether, ethylvinyl ether, propyl vinyl ether, isopropyl vinyl ether, butyl vinylether, isobutyl vinyl ether, sec-butyl vinyl ether, tert-butyl vinylether, pentyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decylvinyl ether, and dodecyl vinyl ether. Those of cyclic vinyl etherinclude cyclopentyl vinyl ether, cyclohexyl vinyl ether, norbornyl vinylether, adamantyl vinyl ether, and butyllactone group-containing vinylether. Those of perfluoroalkyl vinyl ether include perfluoromethyl vinylether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether,perfluoroisopropyl vinyl ether, perfluorobutyl vinyl ether,perfluoroisobutyl vinyl ether, perfluoro-sec-butyl vinyl ether,perfluoro-tert-butyl vinyl ether, perfluoropentyl vinyl ether,perfluorohexyl vinyl ether, perfluorooctyl vinyl ether, andperfluorododecyl vinyl ether. Those of hydroxy group-containing vinylether include hydroxymethyl vinyl ether, 2-hydroxyethyl vinyl ether,3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 5-hydroxypentylvinyl ether, 6-hydroxyhexyl vinyl ether, diethylene glycol monovinylether, polyethylene glycol monovinyl ether, and1,4-cyclohexanedimethanol vinyl ether. Further specific examples ofvinyl ether include ethylhexyl vinyl ether, methoxyethyl vinyl ether,ethoxyethyl vinyl ether, chloroethyl vinyl ether,1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether,diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether,diethylaminoethyl vinyl ether, butylaminoethyl vinyl ether, benzyl vinylether, and tetrahydrofurfuryl vinyl ether.

Specific examples of allyl ethers include methyl allyl ether, ethylallyl ether, propyl allyl ether, butyl allyl ether, benzyl allyl ether,and cyclohexyl allyl ether. Those of hydroxy group-containing allylethers include alkylene glycol monoallyl ethers such as ethylene glycolmonoallyl ether, propylene glycol monoallyl ether, diethylene glycolmonoallyl ether, polyethylene glycol monoallyl ether, and hydroxybutylallyl ether; and allyl ethers of polyhydric alcohols such as glycerolmonoallyl ether.

Further examples include epoxy group-containing vinyl ethers and allylethers. As a β-ketoester group containing vinyl ether or allyl ether, itis possible to cite allyl acetoacetate. Furthermore, it is possible tocite silicon-containing vinyl ethers having a hydrolyzable group, suchas trimethoxysilyl vinyl ether.

Specific examples of allyl esters include allyl acetate, allyl caproate,allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allylbenzoate, allyl acetoacetate, and allyl lactate.

Specific examples of vinyl esters include vinyl butyrate, vinylisobutyrate, vinyl trimethylacetate, vinyl diethylacetate, vinylvalerate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate,vinyl methoxyacetate, vinyl butoxyacetate, vinyl acetoacetate, vinyllactate, vinyl β-phenylbutyrate, and vinyl cyclohexylcarboxylate.

Further examples include dialkyl itaconates, such as dimethyl itaconate,diethyl itaconate and dibutyl itaconate; dialkyl fumarates or monoalkylfumarates, such as dibutyl fumarate; and alkyl vinyl acetates such asethyl vinyl acetate.

Specific examples of olefins include ethylene, propylene andcyclohexene. Those of fluorine-containing olefins include vinylfluoride, vinylidene fluoride, trifluoroethylene,chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene,hexafluoroisobutene, and octafluorocyclopentene.

A styrene compound usable in the present invention is a compound inwhich a vinyl group is bonded to an aromatic ring. Its specific examplesinclude styrene, m- or p-methoxystyrene, m- or p-ethoxystyrene, m- orp-propoxystyrene, m- or p-isopropoxystyrene, m- or p-butoxystyrene, m-or p-tert-butoxystyrene, m- or p-(1-ethoxyethoxy)styrene, m- orp-(1-ethoxypropoxy)styrene, m- or p-(1-isobutoxyethoxy)styrene, m- orp-(2-tetrahydropyranyloxy)styrene, m- orp-tert-butoxycarbonyloxystyrene, m- or p-acetoxystyrene, m- orp-propionyloxystyrene, m- or p-pivaloyloxystyrene, m- orp-benzoyloxystyrene, m- or p-mesyloxystyrene, m- orp-phenylsulfonyloxystyrene, and m- or p-tosyloxystyrene. These styrenecompounds may have at their α-position a halogen atom, alkyl group orfluorine-containing alkyl group.

In the case of introducing the structure of a styrene compound into thefluorine-containing polymer compound, for example,p-butoxycarbonyloxystyrene is copolymerized with the fluorine-containingcompound, and then the butoxycarbonyl moiety may be converted into ahydroxy group.

The norbornene compounds or fluorine-containing norbornene compounds arenorbornene monomers having a monocyclic or polycyclic structure. In theinvention, it is preferable to use a norbornene compound orfluorine-containing norbornene compound obtained by Diels Alder additionreaction between an unsaturated compound (e.g., fluorine-containingolefins, allyl alcohol, fluorine-containing allyl alcohols, acrylicacid, α-fluoroacrylic acid, methacrylic acid, vinyl esters,fluorine-containing vinyl esters, and acrylates, methacrylates,fluorine-containing acrylates and fluorine-containing methacrylates,which are exemplified hereinbefore) and cyclopentadiene orcyclohexadiene.

Specific examples of the acrylamide or methacryloamides includeunsaturated amides such as acrylamide, methacrylamide, N-alkylacrylamideor methacryloamide, where alkyl group is C₁-C₁₀ one (e.g., methyl group,ethyl group, propyl group, butyl group, tert-butyl group, heptyl group,octyl group, cyclohexyl group, and hydroxyethyl group),N,N-dialkylacrylamide or acryloamide, where alkyl group is C₁-C₁₀ one(e.g., methyl group, ethyl group, butyl group, isobutyl group,ethylhexyl group, amd cyclohexyl group),N-hydroxyethyl-N-methylacrylamide or methacryloamide,N-methylolacrylamide, N-methylolmethacrylamide, and diacetoneacrylamide.

Further examples of other comonomers include acrylic acid, methacrylicacid, vinylsulfonic acid, maleic acid, fumaric acid, crotonic acid,itaconic acid, maleimide, acrylonitrile, methacrylonitrile,maleilonitrile, an alkoxysilyl group-containing vinyl silane, andallyloxyethanol.

To conduct a copolymerization for producing the fluorine-containingpolymer compound represented by formula (2), it is preferable to use atleast one of the above-explained acrylates, fluorine-containingacrylates, methacrylates, fluorine-containing methacrylates, styrenecompounds, and fluorine-containing styrene compounds.

Other comonomers are not particularly limited, as long as they arecopolymerizable with the fluorine-containing compound represented byformula (1). For exposure with a high energy ray of 300 nm or shorter,they are preferably free from multiple bond and aromatic ring.

Solvent

As a process for forming the fluorine-containing polymer compoundaccording to the present invention into a thin film, it is possible touse a process having the steps of dissolving the fluorine-containingpolymer compound in an organic solvent, applying the coating solution toa substrate, and drying the film. The organic solvent is notparticularly limited, as long as the fluorine-containing polymercompound is soluble therein. Examples of the organic solvent include (a)ketones such as acetone, methyl ethyl ketone, cyclohexanone, methylisoamyl ketone, and 2-heptanone; (b) polyhydric alcohols and theirderivatives such as ethylene glycol, ethylene glycol monoacetate,diethylene glycol, diethylene glycol monoacetate, propylene glycol,propylene glycol monoacetate, dipropylene glycol, and monomethyl ether,monoethyl ether, monopropyl ether, monobutyl ether or monophenyl etherof dipropylene glycol monoacetate; (c) cyclic ethers such as dioxane;(d) esters such as methyl lactate, ethyl lactate, methyl acetate, ethylacetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; (d) aromatic solventssuch as xylene and toluene; (e) fluorine-containing solvents such aschlorofluorocarbons, alternatives for chlorofluorocarbons, perfluorocompounds, and hexafluoroisopropyl alcohol; (f) terpene-series petroleumnaphtha solvents (high-boiling-point weak solvents) for improvingcoatability; and (g) paraffin-series solvents. These solvents may beused singly or in a mixture of at least two.

Acid Generator

An acid generator used for the resist composition of the presentinvention is not particularly limited. It is possible to select any oneof those used as acid generators of chemically amplified resists.Examples of such acid generators include bissulfonyl diazomethanes,nitrobenzyl derivatives, onium salts, halogen-containing triazinecompounds, cyano group-containing oximesulfonate compounds, and otheroximesulfonate compounds. These photoacid generators may be used singlyor in combination of at least two. Its content may normally be 0.5-20parts by weight, relative to 100 parts by weight of thefluorine-containing polymer compound. If it is less than 0.5 parts byweight, image formation property may become insufficient. It is greaterthan 20 parts by weight, it may be difficult to prepare a homogeneouscoating solution, and its storage stability tends to lower.

Surfactant

It is preferable to contain a surfactant, preferably at least onefluorine-containing and/or silicon-containing surfactant, in the resistcomposition of the present invention. The containment of such surfactantis particularly effective in case that a pattern line width is verynarrow upon using an exposure light source of 250 nm or shorter,particularly 220 nm or shorter, thereby making a resist pattern withgood sensitivity, good resolution, good adhesion to substrate, and fewerdevelopment defects.

Pattern Forming Method

A conventional resist pattern forming method can be used as a method forusing the resist material of the present invention. That is, firstly asolution of the resist material is applied to a substrate such assilicon wafer with a spinner, followed by drying to form aphotosensitive layer. This is exposed to a high-energy ray by anexposure apparatus or the like through a desired mask pattern, followedby heating. Then, this is subjected to a development treatment using adeveloping solution, for example, an alkali aqueous solution such as0.1-10 wt % tetramethylammonium hydroxide aqueous solution. This formingmethod makes it possible to obtain a pattern conforming to the maskpattern. Furthermore, according to need, it is possible to containadditives that are miscible with the resist material, for example,various additives such as additional resins, quencher, plasticizer,stabilizer, coloring agent, surfactant, tackifier, leveling agent,defoaming agent, compatibility enhancing agent, adhesion enhancingagent, and antioxidant.

A high-energy ray used in the present invention is not particularlylimited. In particular, in the case of conducting a fine processing, itis effective to use an exposure device equipped with a short-wavelengthhigh-energy ray (e.g., F₂ excimer laser, ArF excimer laser, KrF excimerlaser, or soft X-ray) generating source. It is effective to use animmersion exposure device that makes it possible to conduct a moreefficient fine processing in numerical aperture and effective wavelengthby using a medium (e.g., water and fluorine-containing solvents), intowhich the used high-energy ray has a less absorption, at a part of theoptical path. The present resist material is also preferable in the caseof use in this device.

Example 1 Synthesis of ethyl 2,2-difluoro-3-hydroxy pentanoaterepresented by the following formula

A 500 mL reactor was charged with 24.2 g (370 mmol, 1.3 eq) of activatedmetallic zinc and 300 mL of tetrahydrofuran (THF) (dehydrated one),followed by adding in a dropwise manner an ethyl bromo-difluoroacetate/THF solution prepared by adding 51.47 g (253.6 mmol, 1.0 eq) ofethyl bromo-difluoro acetate to 80 mL of THF (dehydrated one). After thedropping, stirring was conducted at room temperature for 20 minutes,followed by adding a propionaldehyde/THF solution prepared by adding14.80 g (254.8 mmol, 1.0 eq) of propionaldehyde to 80 mL of THF(dehydrated one), and then stirring at room temperature for 30 minutes.Then, water and diisopropyl ether were added, followed by separation ofan organic layer from an aqueous layer. The obtained organic layer waswashed with diluted hydrochloric acid and water, followed by removingwater with magnesium sulfate, filtration, and distilling the diisopropylether off, thereby obtaining 41.2 g of the target ethyl2,2-difluoro-3-hydroxy pentanoate. The yield was 89%.

The property of ethyl 2,2-difluoro-3-hydroxy pentanoate was as follows.

¹H NMR (CDCl₃) d 4.31 (q, J=7.1 Hz, 2H; CH₂—O), 3.89 (m, 1H; CH—OH),2.50 (br, 1H; OH), 1.71 (m, 1H), 1.52 (m, 1H), 1.32 (t, J=7.1 Hz, 3H;CH₃), 1.02 (t, J=7.3 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −115.26 (d, J=252 Hz, 1F), −122.95 (d, J=252 Hz, 1F)

Example 2 Production of 1-ethoxycarbonyl-1,1-difluoro-2-butylmethacrylate represented by the following formula

A 25 ml reactor was charged with 1.50 g (8.2 mmol) of ethyl2,2-difluoro-3-hydroxypentanoate, 6.5 g of chloroform, 10 mg of anantioxidant NONFLEX MBP made by Seiko Chemical Co., Ltd., 1.03 g (9.9mmol, 1.2 eq) of methacrylic chloride, and 1.25 g (12.4 mmol, 1.5 eq) oftriethylamine, followed by stirring at 55° C. for 4 hours. Then, 10 g ofwater was added, followed by extraction with chloroform one time. Theobtained organic layer was washed with diluted hydrochloric acid andwater, followed by removing water with magnesium sulfate. Afterconducting filtration, chloroform was distilled off, thereby obtaining2.06 g of the target 1-ethoxycarbonyl-1,1-difluoro-2-butyl methacrylate.Purity was 66%, and yield was 66%.

The property of 1-ethoxycarbonyl-1,1-difluoro-2-butyl methacrylate wasas follows.

¹H NMR (CDCl₃) d 6.14 (s, 1H; methylene), 5.62 (s, 1H; methylene), 5.35(m, 1H; CH—O), 4.27 (m, 2H; CH₂—O), 1.93 (s, 3H; CH₃), 1.81 (m, 2H;CH₂), 1.28 (t, J=7.2 Hz, 3H; CH₃), 0.95 (t, J=7.6 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −113.63 (d, J=264 Hz, 1F), −119.57 (d, J=264 Hz, 1F)

Example 3 Production of 1-hydroxycarbonyl-1,1-difluoro-2-butylmethacrylate, methacrylic acid (1), represented by the following formula

A 25 mL reactor was charged with 1.00 g (2.6 mmol) of1-ethoxycarbonyl-1,1-difluoro-2-butyl methacrylate (purity: 66%) and1.00 g of water, followed by cooling to 0° C., adding 1.06 g (4.0 mmol,1.5 eq) of 15 wt % sodium hydroxide aqueous solution in a dropwisemanner, and then stirring at room temperature for 1 hr. The reactionsolution was washed with 10 g of diisopropyl ether. The obtained aqueouslayer was washed with diluted hydrochloric acid, followed by extractionwith diisopropyl ether two times, removal of water with magnesiumsulfate, filtration, and then distilling diisopropyl ether off, therebyobtaining 0.19 g of the target methacrylic acid (1). Upon this, puritywas 78%, and yield was 27%.

The property of methacrylic acid (1) was as follows.

¹H NMR (CDCl₃) d 7.24 (br, 1H; COOH), 6.16 (s, 1H; methylene), 5.63 (s,1H; methylene), 5.39 (m, 1H; CH—O), 1.93 (s, 3H; CH₃), 1.85 (m, 2H;CH₂), 0.97 (t, J=7.6 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −114.24 (d, J=264 Hz, 1F), −119.48 (d, J=264 Hz, 1F)

Example 4 Production of1-(methoxymethyl)oxycarbonyl-1,1-difluoro-2-butyl methacrylate,methacrylate (1), represented by the following formula

Under nitrogen, a 20 mL reactor was charged with 70 mg (0.25 mmol) of1-hydroxycarbonyl-1,1-difluoro-2-butyl methacrylate (purity: 78%) and 3mL of THF (dehydrated one), followed by cooling to 0° C. Then, 65 μL(0.47 mmol, 1.9 eq) was added, followed by stirring at 0° C. for 10 min.Then, 30 μL (0.40 mmol, 1.6 eq) of chloromethyl methyl ether was added,followed by stirring at 0° C. for 20 min. Then, 5 mL of water was addedto the reaction solution, followed by extraction with diisopropyl ethertwo times and removal of water with magnesium sulfate. After conductingfiltration, diisopropyl ether was distilled off, thereby obtaining 58 mgof the target 1-(methoxymethyl)oxycarbonyl-1,1-difluoro-2-butylmethacrylate. Upon this, purity was 96%, and yield was 83%.

The property of 1-(methoxymethyl)oxycarbonyl-1,1-difluoro-2-butylmethacrylate was as follows.

¹H NMR (CDCl₃) d6.15 (m, 1H; methylene), 5.63 (m, 1H; methylene),5.30-5.45 (m, 3H, CH—O, CH₂), 3.47 (s, 3H; CH₃), 1.93 (s, 3H; CH₃), 1.85(m, 2H; CH₂), 0.97 (t, J=7.6 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −113.62 (d, J=264 Hz, 1F), −119.51 (d, J=264 Hz, 1F)

¹³C NMR (CDCl₃) d 9.7, 18.5, 21.2, 58.6, 73.0, 93.2, 113.6, 127.4,135.5, 162.7, 166.3

Example 5 Production of t-butyl 2,2-difluoro-3-hydroxypentanoaterepresented by the following formula

A 100 mL reactor was charged with 2.10 g (32.1 mmol, 1.5 eq) ofactivated metallic zinc and 30 mL of THF (dehydrated one), followed byadding in a dropwise manner a t-butyl bromo-difluoro acetate/THFsolution prepared by adding 5.0 g (21.6 mmol, 1.0 eq) of t-butylbromo-difluoro acetate to 10 mL of THF (dehydrated one). After thedropping, stirring was conducted at room temperature for 1 hr, followedby adding a propionaldehyde/THF solution prepared by adding 1.25 g (21.5mmol, 1.0 eq) of propionaldehyde to 10 mL of THF (dehydrated one), andthen stirring at room temperature for 30 minutes. Then, water anddiisopropyl ether were added, followed by separation of an organic layerfrom an aqueous layer. The obtained organic layer was washed withdiluted hydrochloric acid and water, followed by removing water withmagnesium sulfate, filtration, and distilling the diisopropyl ether off,thereby obtaining 3.59 g of the target t-butyl 2,2-difluoro-3-hydroxypentanoate. Upon this, purity was 80%, and yield was 70%.

The property of t-butyl 2,2-difluoro-3-hydroxy pentanoate was asfollows.

¹H NMR (CDCl₃) d 3.85 (m, 1H; CH—OH), 2.80 (br, 1H; OH), 1.60 (m, 2H;CH₂), 1.50 (m, 9H; CH₃), 1.02 (t, J=7.6 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −115.87 (dd, J=7.3 Hz, 261 Hz, 1F), −122.47 (dd,J=14.6 Hz, 263 Hz, 1F)

Example 6 Production of 1-(t-butoxycarbonyl)-1,1-difluoro-2-butylmethacrylate, methacrylate (2), represented by the following formula

A 25 mL reactor was charged with 1.50 g (5.6 mmol) of t-butyl2,2-difluoro-3-hydroxypentanoate and 15 mL of chloroform, 10 mg ofNONFLEX MBP, 1.17 g (11.2 mmol, 2 eq) of methacrylic chloride, and 0.87g (8.6 mmol, 1.5 eq) of triethylamine, followed by stirring at 55° C.for 24 hr. Then, 15 mL of water was added, followed by extraction withchloroform one time. The obtained organic layer was washed withsaturated sodium hydrogencarbonate and water, followed by removal ofwater with magnesium sulfate. After conducting filtration, chloroformwas distilled off, thereby obtaining 1.57 g of the target1-(t-butoxycarbonyl)-1,1-difluoro-2-butyl methacrylate. Upon this,purity was 58%, and yield was 58%.

The property of 1-(t-butoxycarbonyl)-1,1-difluoro-2-butyl methacrylatewas as follows.

¹H NMR (CDCl₃) d 6.15 (s, 1H; methylene), 5.62 (m, 1H; methylene), 5.36(m, 1H; CH—O), 1.93 (s, 3H; CH₃), 1.78 (m, 2H; CH₂), 1.46 (s, 3H; CH₃),0.95 (t, J=7.6 Hz, 3H; CH₃)

¹⁹F NMR (CDCl₃) d −113.15 (dd, J=7.3 Hz, 261 Hz, 1F), −120.17 (dd,J=14.6 Hz, 261 Hz, 1F)

Example 7 Synthesis of Fluorine-Containing Polymer Compound (1), asShown in the Following Formula

A 100 mL round-bottom flask equipped with a reflux condenser and astirrer was charged with 6.00 g of methacrylate (1), 0.11 g ofazobisisobutyronitrile (AIBN), and 15.0 mL of methyl ethyl ketone,followed by replacing the inside of the flask with nitrogen. While theflask was heated in an oil bath at 60° C., stirring was conducted for 18hr to conduct the reaction. After the reaction, 60 ml of n-hexane wasadded, followed by stirring. The resulting precipitate was taken out ofthe flask, followed by drying at 55° C. for 18 hr, thereby obtaining4.40 g of fluorine-containing polymer compound (1) in a white solid.Yield was 73%. The molecular weight was determined by gel permeationchromatography (GPC; standard substance: polystyrene). The results areshown in Table 1.

Example 8 Synthesis of Fluorine-Containing Polymer Compound (2), asShown in the Following Formula

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, methacrylate (1) and MA-lactone (made by OSAKAORGANIC CHEMICAL INDUSTRY LTD.), thereby synthesizingfluorine-containing polymer compound (2) in a white solid. The molecularweight was determined by GPC (standard substance: polystyrene). Thecompositional molar ratio (a/b) of fluorine-containing polymer compound(2) was determined by NMR. The results are shown in Table 1.

Example 9 Synthesis of Fluorine-Containing Polymer Compound (3), asShown in the Following Formula

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, methacrylate (2) and hydroxyadamantylmethacrylate (MA-HMA made by DAICEL CHEMICAL INDUSTRIES, LTD.), therebysynthesizing fluorine-containing polymer compound (3) in a white solid.The molecular weight was determined by GPC (standard substance:polystyrene). The compositional molar ratio (a/b) of fluorine-containingpolymer compound (3) was determined by NMR. The results are shown inTable 1.

Example 10 Synthesis of Fluorine-Containing Polymer Compound (4), asShown in the Following Formula

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, methacrylate (1) and MA-BTHB-NB synthesized bythe process according to Japanese Patent Application Publication2004-175740, of which disclosure is incorporated herein by reference,thereby synthesizing fluorine-containing polymer compound (4) in a whitesolid. The molecular weight was determined by GPC (standard substance:polystyrene). The compositional molar ratio (a/b) of fluorine-containingpolymer compound (4) was determined by NMR. The results are shown inTable 1.

Example 11

1. Synthesis of MA-3,5-HFA-CHOH Represented by the Following Formula

A 2 L, three-necked flask equipped at its top with a reflux condenserwas charged with 100 g of 3,5-HFA-CHOH, which had been synthesized bythe process according to Japanese Patent Application Publication2004-083900, corresponding to U.S. Pat. No. 7,125,943, of whichdisclosure is incorporated herein by reference, and which is representedby the following formula,

23.8 g of methacrylic acid, 22.0 g of methanesulfonic acid, and 500 mLof toluene, followed by heating under reflux in an oil bath at 130° C.for 3.5 hr. After the reaction, the reaction solution was poured intosaturated sodium bicarbonate water for neutralization, followed byadding 1 L of toluene and collecting the toluene layer. The obtainedtoluene solution was concentrated, followed by recrystallization,thereby obtaining 78.0 g of MA-3,5-HFA-CHOH.

2. Synthesis of Fluorine-Containing Polymer Compound (5), as Shown inthe Following Formula

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, methacrylate (1) and MA-3,5-HFA-CHOH, therebysynthesizing fluorine-containing polymer compound (5) in a white solid.The molecular weight was determined by GPC (standard substance:polystyrene). The compositional molar ratio (a/b) of fluorine-containingpolymer compound (5) was determined by NMR. The results are shown inTable 1.

TABLE 1 Fluorine- containing Molecular Copolymerization Polymer WeightMw Ratio Compound (Mw/Mn) (a/b) Ex. 7 (1) 17,000 (2.41) — Ex. 8 (2)18,000 (2.25) 51/49 Ex. 9 (3) 17,500 (2.15) 52/48 Ex. 10 (4) 16,800(1.98) 49/51 Ex. 11 (5) 15,900 (2.02) 85/15

Example 12

Fluorine-containing polymer compounds (1), (2), (3), (4) and (5) wereeach dissolved in propylene glycol methyl acetate, and they wereadjusted to have a solid matter content of 14%. Furthermore,triphenylsulfonium triflate (TPS105) made by Midori Kagaku Co., Ltd. asan acid generator was dissolved in a manner to be 5 parts by weight per100 parts by weight of the polymer compound, thereby preparing resistcompositions (R-1, R-2, R-3, R-4 and R-5).

Then, all of the resist compositions were filtered with a membrane filerof a pore diameter of 0.2 μm. Then, each composition was applied to asilicon wafer by spin coating to obtain a resist film of a filmthickness of 250 nm. After conducting a preliminary baking at 120° C.,an exposure to a 193 nm ultraviolet ray was conducted through aphotomask of a 130 nm-size, 1:1 line-and-space (130 nm1L/1S pattern).Then, a post exposure baking was conducted at 120° C. Then, adevelopment was conducted at 22° C. for 1 minute using 2.38 wt %tetramethylammonium hydroxide aqueous solution. As a result, ahigh-resolution pattern was obtained from each resist composition. Therewere almost not found inferiority defect in adhesion to substrate,film-forming inferiority defect, development defect, and etchingresistance inferiority defect.

The 130 nm1L/1S pattern resolved at the optimum exposure was observed bya critical dimension scanning electron microscope (CD-SEM), S9220(tradename) of Hitachi High-Technologies Corporation. The results of theevaluation of the patterns, based on that of the resist composition R-1,are shown in Table 2.

TABLE 2 Pattern Polymer Compound Characteristic Example 12 ResistComposition R-1 Fluorine-containing Polymer Slightly Swelled Compound(1) R-2 Fluorine-containing Polymer Rectangular Compound (2) R-3Fluorine-containing Polymer Rectangular Compound (3) R-4Fluorine-containing Polymer Rectangular Compound (4) R-5Fluorine-containing Polymer Rectangular Compound (5) Com. Ex. 1 PolymerCompound (6) Swelled Com. Ex. 2 Polymer Compound (7) Swelled Com. Ex. 3Polymer Compound (8) Swelled Com. Ex. 4 Polymer Compound (9) Swelled

COMPARATIVE EXAMPLE 1

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, tert-butyl methacrylate and MA-lactone (made byOSAKA ORGANIC CHEMICAL INDUSTRY LTD.), thereby synthesizing polymercompound (6) (see the following formula).

Then, a resist composition and a resist pattern were prepared frompolymer compound (6) by the same process as that of Example 12. Theresult of the evaluation is shown in Table 2.

COMPARATIVE EXAMPLE 2

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, methyladamantyl methacrylate (MA-MAD, made byDAICEL CHEMICAL INDUSTRIES, LTD.) and hydroxyadamantyl methacrylate(MA-HMA, made by DAICEL CHEMICAL INDUSTRIES, LTD.), thereby synthesizingpolymer compound (7) (see the following formula).

Then, a resist composition and a resist pattern were prepared frompolymer compound (7) by the same process as that of Example 12. Theresult of the evaluation is shown in Table 2.

COMPARATIVE EXAMPLE 3

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, tert-butyl methacrylate and MA-BTHB-NB, therebysynthesizing polymer compound (8) (see the following formula).

Then, a resist composition and a resist pattern were prepared frompolymer compound (8) by the same process as that of Example 12. Theresult of the evaluation is shown in Table 2.

COMPARATIVE EXAMPLE 4

Similar to the process of Example 7, a copolymerization was conducted byusing two raw materials, MA-MAD (made by DAICEL CHEMICAL INDUSTRIES,LTD.) and MA-3,5-HFA-CHOH, thereby synthesizing polymer compound (9)(see the following formula).

Then, a resist composition and a resist pattern were prepared frompolymer compound (9) by the same process as that of Example 12. Theresult of the evaluation is shown in Table 2.

As is clear from Table 2, the resist compositions R-1 to R-5 accordingto the present invention provided good results (i.e., rectangularpatterns with no or slight swelling, as compared with those ofComparative Examples 1 to 4.

In other words, it is possible to prepare a resist composition thatresponds to a high-energy ray (e.g., far-ultraviolet ray such as KrFexcimer laser (wavelength: 248 nm) or ArF excimer laser (wavelength: 193nm)) by using a fluorine-containing polymer compound of the presentinvention. Furthermore, such resist composition is superior in patternrectangularity as a chemically amplified resist composition bycontaining an acid-labile protecting group (e.g., acetal group).Therefore, it can extremely preferably be used in the production ofintegrated circuit devices that are expected in the future to have finersizes.

What is claimed is:
 1. A fluorine-containing compound is selected fromthe group consisting of:

wherein R² represents an acid-labile protecting group, R³ represents afluorine atom or a fluorine-containing alkyl group, R⁷ represents ahydrogen atom or a straight-chain, branched or cyclic alkyl orfluoroalkyl group, R⁸ represents a straight-chain, branched or cyclicalkyl or fluoroalkyl group, and R⁷ and R⁸ may be combined to form aring.
 2. A fluorine-containing compound according to claim 1, wherein R³represents a fluorine atom.
 3. A fluorine-containing compound accordingto claim 1, wherein R⁷ and R⁸ each independently represent a C₁-C₄straight-chain or branched alkyl or fluoroalkyl group or a C₃-C₁₀ cyclicalkyl or fluoroalkyl group, or R⁷ and R⁸ are bonded together to form aC₄-C₈ alicyclic hydrocarbon group.
 4. A fluorine-containing compoundaccording to claim 1, wherein R⁷ represents a hydrogen atom or amonovalent organic group selected from the group consisting of methylgroup, ethyl group, propyl group, butyl group, cyclopentyl group,cyclohexyl group, norbornyl group, adamantyl group, trifluoromethylgroup, 2,2,2-trifluoroethyl group, 1-(trifluoromethyl)ethyl group, and3,3,3-trifluoropropyl group, R⁸ represents a monovalent organic groupselected from the group consisting of methyl group, ethyl group, propylgroup, butyl group, cyclopentyl group, cyclohexyl group, norbornylgroup, adamantyl group, trifluoromethyl group, 2,2,2-trifluoroethylgroup, 1-(trifluoromethyl)ethyl group, and 3,3,3-trifluoropropyl group,or R⁷ and R⁸ are bonded together to form a cyclopentyl group, cyclohexylgroup or cycloheptyl group.
 5. A fluorine-containing compound accordingto claim 4, wherein R³ represents a fluorine atom.
 6. Afluorine-containing compound according to claim 1, which is representedby one of the following formulas,

wherein R² is defined as in claim
 1. 7. A fluorine-containing compoundaccording to claim 1, wherein R² is a monovalent organic group selectedfrom the group consisting of R¹¹—O—C(═O)—, R¹¹—O—CHR¹²—, CR¹³R¹⁴R¹⁵—,SiR¹³R¹⁴R¹⁵—, and R¹¹—C(═O)—, where R¹¹ represents an alkyl group,alicyclic hydrocarbon group, or aryl group; R¹² represents a hydrogenatom, alkyl group, alicyclic hydrocarbon group, alkenyl group, aralkylgroup, alkoxy group, or aryl group; R¹³, R¹⁴ and R¹⁵ each independentlyrepresent an alkyl group, alicyclic hydrocarbon group, alkenyl group,aralkyl group, or aryl group; and at least two groups of R¹³, R¹⁴ andR¹⁵ may be combined to form a ring.
 8. A fluorine-containing compoundaccording to claim 1, wherein R² represents a methoxymethyl or t-butylgroup.